The first signal received from the Rosetta spacecraft ESA’s Operations Centre in Darmstadt, Germany on 20 January 2014. Rosetta had woken up 807 million km away after 31 months of deep-space hibernation.

Rosetta is chasing Comet 67P/Churyumov–Gerasimenko, where it will become the first mission to rendezvous with a comet, the first to land on a comet and the first to follow a comet around the Sun.

Mission controllers cheer the first signal received from the Rosetta spacecraft on 20 January 2014. Rosetta had woken up 807 million km away after 31 months of deep-space hibernation. At ESA’s Operations Centre in Darmstadt, Germany, mission controllers, ESA staff and press waited for the first sign of Rosetta’s revival.

Rosetta is chasing Comet 67P/Churyumov–Gerasimenko, where it will become the first mission to rendezvous with a comet, the first to land on a comet and the first to follow a comet around the Sun.

From left to right: Alvaro Giménez, ESA Director of Science and Robotic Exploration, Thomas Reiter, ESA Director of Human Spaceflight and Operations, Jan-Dietrich Wörner from DLR and Chair of the ESA Council, and Paolo Ferri, Head of Mission Operations at ESA's European Space Operations Centre at Darmstadt, Germany.

Rosetta’s journey from launch in March 2004 to comet 67P/Churyumov-Gerasimenko in August 2014, including 3 flybys of Earth and 1 of Mars. By January 2014 Rosetta is about 9 million kilometres from comet 67P/CG. By early May, Rosetta will be 2 million kilometres from the comet and at the end of May the spacecraft will execute a major rendezvous manoeuvre to line it up for orbit insertion at the start of August.

After an extensive mapping phase by the orbiter in August–September 2014, a landing site will be selected on Comet 67P/Churyumov–Gerasimenko for Philae to conduct in situ measurements in November 2014.

Rosetta is a highly ambitious mission that will take on unprecedented operational, scientific and engineering challenges.

Until the final approach of Rosetta, the position and orbit of Comet 67P/Churyumov-Gerasimenko are only known to within 10 000 km. The spacecraft itself will provide images and data in May 2014 from 2 million km away to improve the knowledge of the comet’s position. Nine separate, complex manoeuvres must be carried out to gradually reduce distance and speed.

In August and September 2014, from an altitude of about 25 km above the comet, an extensive mapping phase of its 4 km wide nucleus will help select 5 possible landing sites for Philae in November 2014. Once locked onto the nucleus, Philae will relay data back to the orbiter for transmission to Earth.

The orbiter will then stay alongside the comet as it rushes toward the inner Solar System at speeds of over 100 000 km/h, collecting dust and gas samples and monitoring the ever-changing conditions as the comet warms up.

Rosetta will be operated by a mission control team at ESA’s European Space Operations Centre in Germany, who will make crucial adjustments to manoeuvres at each stage of the journey, in particular during the final rendezvous with the comet’s nucleus. They will be supported by a science operations team at ESA’s European Space Astronomy Centre in Spain. Philae will be operated by the German Aerospace Centre DLR, supported by the lander science operations team from the French space agency CNES. All Philae commands will be sent to the spacecraft via ESOC.

Rosetta marks several firsts in space exploration. It is the first mission to journey beyond the main asteroid belt relying solely on solar cells for power generation, allowing it to operate 800 million km from the Sun, where levels of sunlight are only 4% of those received by Earth. Rosetta’s electric power generation was based on a new technology of very high-efficiency solar cells known as LILT cells, standing for Low Intensity, Low Temperature.

Rosetta will cover a huge range of distances from the Sun, from its launch to the colder, outer reaches of the Solar System and back, so temperature control inside the spacecraft is critical. When the spacecraft is near the Sun, overheating has been prevented by using special radiators to dissipate surplus heat into space. In the outer Solar System, where temperatures are very low, the hardware must be kept warm. This was achieved by locating heaters at strategic points, placing louvres over the radiators, and wrapping the spacecraft in multi-layered insulation blankets to cut down on heat loss.

The greatest challenge was to ensure that Rosetta survived the hazards of travelling through deep space for more than 10 years. Knowhow gained from telecommunication satellites, which have a nominal life time of over 10 years, was critical input in the preparatory phase of the spacecraft, and engineers conducted highly stringent pre-launch tests to confirm Rosetta's endurance.

Scientific consortia from institutes across Europe and the United States provided the different instruments of the orbiter. Rosetta’s industrial team involved more than 50 contractors from 14 European countries and the USA. The prime spacecraft contractor was Astrium Germany. Major subcontractors were Astrium UK who built the spacecraft platform, Astrium France who supplied the spacecraft avionics and Alcatel Alenia Spazio for assembly, integration and verification.

Rosetta's 11 instruments include several cameras, spectrometers and a number of sensors and experiments:

Surrounded by four 100-m lightning towers, the first Ariane 5G+, atop its mobile launch platform, stands on the pad at the Launch Zone (ZL-3) of the Ariane Launch Complex no.3 (ELA-3) at the Guiana Space Centre, Europe's space port, on the evening of February 24, 2004, during final preparation for a first launch attempt two days later.

Selected in November 1993 as a "Cornerstone" mission of ESA's long-term science program "Horizon 2000", the Rosetta probe was initially planned for launch on the V158 flight in January 2003 for an eight-year journey to the comet 46P/Wirtanen. Due to delays in the Ariane 5 program, the initial launch campaign was interrupted in December 2002 and the mission was redesigned for a launch toward the comet 67P/Churyumov-Gerasimenko.
Build by EADS Astrium, the Rosetta probe consists in a 3,065-kg spacecraft (1,578-kg dry mass) designed to enter orbit around the comet's nucleus in August 2014 after a series of gravity assist manoeuvres to gain enough orbital energy, flying three times by Earth (March 2005, November 2007 and November 2009) and once by Mars (February 2007). En route to the comet, the probe will flyby the asteroids 2867 Steins (September 2008) and 21 Lutetia (July 2010). The spacecraft will map the comet's surface in fine detail and land a package of instruments (the Rosetta Lander) to study some of the most primitive, unprocessed material in the solar system. The mission will provide clues to the physical and chemical processes that marked the systems beginning 4.6 billion years ago.

Credits: ESA–S. Corvaja

Rosetta and Philae

Rosetta was launched in 2004 and has since travelled around the Sun five times, picking up energy from Earth and Mars to line it up with its final destination: comet 67P/Churyumov–Gerasimenko. For the coldest, loneliest leg of the mission, as Rosetta travelled out towards the orbit of Jupiter, the spacecraft was put into deep-space hibernation.

In 2014, Rosetta will complete its cruise towards the comet, rendezvousing with it in August, before putting its Philae lander onto the comet’s surface in November, as it begins its journey closer to the Sun.

The time for Rosetta to wake up and prepare for this most exciting scientific adventure is now fast approaching. The spacecraft’s internal alarm clock is set for 10:00 GMT (11:00 CET) on 20 January. Once it has warmed itself up, it should re-establish communication with Earth several hours later.